Imperial College London

Professor Norbert Hoffmann

Faculty of EngineeringDepartment of Mechanical Engineering

Visiting Professor
 
 
 
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Contact

 

n.hoffmann

 
 
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Location

 

557City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

123 results found

Fontanela F, Grolet A, Salles L, Chabchoub A, Hoffmann Net al., 2018, Dark solitons, modulation instability and breathers in a chain of weakly nonlinear oscillators with cyclic symmetry, JOURNAL OF SOUND AND VIBRATION, Vol: 413, Pages: 467-481, ISSN: 0022-460X

JOURNAL ARTICLE

Koellisch N, Behrendt J, Klein M, Hoffmann Net al., 2018, Nonlinear real time prediction of ocean surface waves, OCEAN ENGINEERING, Vol: 157, Pages: 387-400, ISSN: 0029-8018

JOURNAL ARTICLE

Oberst S, Baetz J, Campbell G, Lampe F, Leis JCS, Hoffmann N, Morlock Met al., 2018, Vibro-acoustic and nonlinear analysis of cadavric femoral bone impaction in cavity preparations, International Conference on Engineering Vibration (ICoEV), Publisher: E D P SCIENCES, ISSN: 2261-236X

CONFERENCE PAPER

Papangelo A, Hoffmann N, Grolet A, Stender M, Ciavarella Met al., 2018, Multiple spatially localized dynamical states in friction-excited oscillator chains, JOURNAL OF SOUND AND VIBRATION, Vol: 417, Pages: 56-64, ISSN: 0022-460X

JOURNAL ARTICLE

Stender M, Tiedemann M, Hoffmann N, Oberst Set al., 2018, Impact of an irregular friction formulation on dynamics of a minimal model for brake squeal, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, Vol: 107, Pages: 439-451, ISSN: 0888-3270

JOURNAL ARTICLE

Hadjihoseini A, Lind PG, Mori N, Hoffmann NP, Peinke Jet al., 2017, Rogue waves and entropy consumption, EPL, Vol: 120, ISSN: 0295-5075

JOURNAL ARTICLE

Oberst S, Marburg S, Hoffmann N, 2017, Determining periodic orbits via nonlinear filtering and recurrence spectra in the presence of noise, 10th International Conference on Structural Dynamics (EURODYN), Publisher: ELSEVIER SCIENCE BV, Pages: 772-777, ISSN: 1877-7058

CONFERENCE PAPER

Papangelo A, Ciavarella M, Hoffmann N, 2017, Subcritical bifurcation in a self-excited single-degree-of-freedom system with velocity weakening-strengthening friction law: analytical results and comparison with experiments, NONLINEAR DYNAMICS, Vol: 90, Pages: 2037-2046, ISSN: 0924-090X

JOURNAL ARTICLE

Papangelo A, Grolet A, Salles L, Hoffmann N, Ciavarella Met al., 2017, Snaking bifurcations in a self-excited oscillator chain with cyclic symmetry, COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION, Vol: 44, Pages: 108-119, ISSN: 1007-5704

JOURNAL ARTICLE

Papangelo A, Hoffmann N, Ciavarella M, 2017, Load-separation curves for the contact of self-affine rough surfaces, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322

JOURNAL ARTICLE

Grolet A, Hoffmann N, Thouverez F, Schwingshackl Cet al., 2016, Travelling and standing envelope solitons in discrete non-linear cyclic structures, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, Vol: 81, Pages: 75-87, ISSN: 0888-3270

JOURNAL ARTICLE

Hadjihosseini A, Waechter M, Hoffmann NP, Peinke Jet al., 2016, Capturing rogue waves by multi-point statistics, NEW JOURNAL OF PHYSICS, Vol: 18, ISSN: 1367-2630

JOURNAL ARTICLE

Oberst S, Zhang Z, Campbell G, Morlock M, Lai JCS, Hoffmann Net al., 2016, Towards the understanding of hip squeak in total hip arthroplasty using analytical contact models with uncertainty, INTER-NOISE 2016, Pages: 5539-5549

© 2016, German Acoustical Society (DEGA). All rights reserved. Osteoarthritis in hip joints affects patients' quality of life such that often only costly orthopaedic surgeries i.e. total hip arthroplasty (THA) provide relief. Common implant materials are metal alloys, steel or titanium-based, plastics such as ultra-high molecular weight polyethylene, or biocompatible alumina and composite ceramics. Hard-on-hard (HoH) bearing articulations, i.e. ceramic-on-ceramic, or hard-on-soft combinations are used. HoH implants have been known to suffer from squeaking, a phenomenon commonly encountered in friction-induced self-excited vibrations. However, the frictional contact mechanics, its dynamics related to impingement, the effect of socket position, stem configuration, bearing size and patient characteristics are poorly understood. This study gives an overview of the state of the art biomechanical research related to squeaking in THA, with a focus on the effects of friction, stability, related wear and lubrication. An analytical model is proposed to study the onset of friction-induced vibrations in a simplified hemispherical hip stem rubbing in its bearing by varying the contact area. Preliminary results of the complex eigenvalue analysis and stick-slip motion analysis indicate that an increased contact fosters the development of instabilities, even at very small values of the friction coefficient owing to large local contact pressures.

CONFERENCE PAPER

Salles L, Staples B, Hoffmann N, Schwingshackl Cet al., 2016, Continuation techniques for analysis of whole aeroengine dynamics with imperfect bifurcations and isolated solutions, NONLINEAR DYNAMICS, Vol: 86, Pages: 1897-1911, ISSN: 0924-090X

JOURNAL ARTICLE

Akhmediev N, Soto-Crespo JM, Devine N, Hoffmann NPet al., 2015, Rogue wave spectra of the Sasa-Satsuma equation, PHYSICA D-NONLINEAR PHENOMENA, Vol: 294, Pages: 37-42, ISSN: 0167-2789

JOURNAL ARTICLE

Grolet A, Hoffmann NP, Schwingshackl C, 2015, Solitons in Non-Linear Cyclic Systems, Euromech Colloquium 573: Coupling and Nonlinear Interactions in Rotating Machinery

CONFERENCE PAPER

Kruse S, Tiedemann M, Zeumer B, Reuss P, Hetzler H, Hoffmann Net al., 2015, The influence of joints on friction induced vibration in brake squeal, JOURNAL OF SOUND AND VIBRATION, Vol: 340, Pages: 239-252, ISSN: 0022-460X

JOURNAL ARTICLE

Kruse S, Tiedemann M, Zeumer B, Reuss P, Hetzler H, Hoffmann Net al., 2015, The influence of joints on friction induced vibration in brake squeal (vol 340, pg 239, 2014), JOURNAL OF SOUND AND VIBRATION, Vol: 351, Pages: 311-312, ISSN: 0022-460X

JOURNAL ARTICLE

Peric R, Hoffmann N, Chabchou A, 2015, Initial wave breaking dynamics of Peregrine-type rogue waves: A numerical and experimental study, EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, Vol: 49, Pages: 71-76, ISSN: 0997-7546

JOURNAL ARTICLE

Tiedemann M, Kruse S, Hoffmann N, 2015, Dominant damping effects in friction brake noise, vibration and harshness: the relevance of joints, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING, Vol: 229, Pages: 728-734, ISSN: 0954-4070

JOURNAL ARTICLE

Akhmediev N, Soto-Crespo JM, Devine N, Hoffmann NPet al., 2014, Rogue waves of the Sasa-Satsuma equation in a chaotic wave field

CONFERENCE PAPER

Akhmediev N, Soto-Crespo JM, Devine N, Hoffmann NPet al., 2014, Rogue waves of the Sasa-Satsuma equation in a chaotic wave field

CONFERENCE PAPER

Chabchoub A, Kimmoun O, Branger H, Kharif C, Hoffmann N, Onorato M, Akhmediev Net al., 2014, Gray solitons on the surface of water, PHYSICAL REVIEW E, Vol: 89, ISSN: 2470-0045

JOURNAL ARTICLE

Chabchoub A, Peric R, Hoffmann NP, 2014, DYNAMICS OF UNSTABLE STOKES WAVES: A NUMERICAL AND EXPERIMENTAL STUDY, 33rd ASME International Conference on Ocean, Offshore and Arctic Engineering, Publisher: AMER SOC MECHANICAL ENGINEERS

CONFERENCE PAPER

Gräbner N, Tiedemann M, Von Wagner U, Hoffmann Net al., 2014, Nonlinearities in Friction Brake NVH - Experimental and Numerical Studies

Copyright © 2014 SAE International. Industry and academia agree that brake squeal is a nonlinear phenomenon. Consequently, using solely linear finite-element (FE) models and assessing the tendency of a brake system to squeal exclusively on the stability of the trivial solution is not appropriate. However, the latter approach - in the brake community known as complex eigenvalue analysis (CEA) - is extensively used in industry. Until now, nonlinear simulation approaches considering existence and stability of periodic solutions are mostly limited to minimal models. Among the variety of reasons for this the complexity of large-scale nonlinear models as well as the identification of nonlinear material and system parameters are crucial. This contribution discusses the relevance of nonlinearities in friction brake noise, vibration, harshness (NVH) and presents a novel simulation approach for brake squeal. On the basis of experimental results it is pointed out that the consideration of nonlinearities in simulation as well as new methods for numerical studies are necessary to cope with the system-inherent phenomena. After presenting experimental methods to characterize nonlinearities in brake systems, a novel simulation approach for brake squeal is introduced. This approach is based on subspace projection and allows the calculation of limit cycles considering nonlinearities such as joint damping. Studies are conducted for minimal models and a full-scale industrial FE model.

CONFERENCE PAPER

Hadjihosseini A, Peinke J, Hoffmann NP, 2014, Stochastic analysis of ocean wave states with and without rogue waves, NEW JOURNAL OF PHYSICS, Vol: 16, ISSN: 1367-2630

JOURNAL ARTICLE

Hoffmann NP, Bechthold J, Ziemer G, Evers K-U, Jochmann Pet al., 2014, Study of Local Ice Pressure Distribution on a Cylindrical Offshore Structure by Using Tactile Sensors., 22nd IAHR International Symposium on Ice

CONFERENCE PAPER

Kruse S, Hoffmann N, 2014, On the robustness of mode-coupling instabilities in friction induced systems, IEEE Global Communications Conference (GLOBECOM), Publisher: IEEE, Pages: 2939-2944, ISSN: 1930-529X

CONFERENCE PAPER

Kruse S, Stingl B, Hieke J, Papangelo A, Tiedemann M, Hoffmann N, Ciavarella Met al., 2014, The influence of loading conditions on the static coefficient of friction: A study on brake creep groan, Pages: 149-160, ISSN: 2191-5644

© The Society for Experimental Mechanics, Inc. 2014. This work focuses on the phenomenon of creep groan in brake systems as a problem leading to customer complaints (Kinkaid et al., J Sound Vib 267:105–166, 2003). It is potentially induced by a stick-slip phenomenon in the friction interface, but the dynamics are not well understood yet. This work tries to contribute to the understanding of the excitation mechanisms, the interaction of different length scales and possible measures to influence the phenomenon. It presents a dual—based on simulation and experiment—approach to investigate the phenomenon employing works of Ben-David and Fineberg (Phys Rev Lett 106, 2011) and Bar Sinai et al. (Geophys Res Lett 39, 2011). On the one side using the approach of Bar Sinai et al. (Geophys Res Lett 39, 2011) a one-dimensional simulation model is built up based on the contact state evolution of a representative brake pad and disc couple. This model is used to describe the interface dynamics while taking into account the surrounding simplified loading geometry. Parallel to this approach an experimental setup with a simplified disc brake is built up. As the simulation model allows to predict the level of the average static friction coefficient for different load cases, the simple test setup allows a validation. The experimental results show that the static friction coefficient can be systematically changed by modification of the loading geometry while one still observes the perturbing influence of uncontrolled process parameters.

CONFERENCE PAPER

Papangelo A, Stingl B, Hoffmann NP, Ciavarella Met al., 2014, A simple model for friction detachment at an interface of finite size mimicking Fineberg's experiments on uneven loading, PHYSICAL MESOMECHANICS, Vol: 17, Pages: 311-320, ISSN: 1029-9599

JOURNAL ARTICLE

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